This invention relates to a photosensitive composition and a process for forming a pattern with the composition.
The inside surface of a face plate of a color picture tube is coated with three kinds of phosphors either dot-wise or stripe-wise. According to the conventional process the phosphors are coated as follows: a mixture of a first phosphor and a photosensitive resin is at first applied to the inside surface of a face plate and dried to form a coating. Then, the coating is irradiated with an ultraviolet ray through shadow mask openings. The positions of the ultraviolet irradiation correspond to the positions which electron beams hit to cause the phosphor to emit light, that is, to the positions at which the phosphor is fixed. The irradiated photosensitive resin is insolubilized due to the irradiation, and the coating at all those positions is insolubilized thereby. Then, the coating is washed with a solvent to retain only the insolubilized portions on the face plate and remove other portions by dissolution. Then, the similar treatment is carried out with a mixture of a second phosphor and a photosensitive resin, and then with a mixture of a third phosphor and a photosensitive resin.
As is obvious from the foregoing, a process for preparing the phosphor screen of a color picture tube requires repetitions of a series of wet applications, water washing and drying, and thus is complicated. Its simplication has been very keenly desired.
To this end, some of the present inventors proposed a process for forming a phosphor screen involving considerably simpler steps than before [see particularly Japanese Patent Application Kokai (laid-open) No. 126861/78], which was established on the basis of a new finding that a photolytic product of an aromatic diazonium salt has a capacity to accept power particles. The process is characterized by (1) applying a photosensitive composition that contains an aromatic diazonium salt as a photosensitive component and that turns sticky by light exposure to a substrate surface to obtain a thin layer, (2) subjecting the thin layer to a pattern wise light exposure to turn the exposed portions sticky, and (3) contacting the light-exposed thin layer with power particles to allow the thin layer to accept the powder particles, where only repetitions of light exposure and contacting with powder particles suffice for the second and third phosphors and once a coating is formed patterns of any kind of phosphor can be obtained.
However, the sensitivity of the photosensitive component of the process is somewhat lower than that of the conventional photosensitive resin, and thus the process has the problem of a prolonged treating time.